Sterilization of various materials by irradiation with high-energy radiation (gamma and X-ray) is a well-established technology. High-energy irradiation can break molecular bonds in various materials and decompose the toxic compounds into more benign compounds. Gamma sterilization has been considered the norm up until now because of the high energy and fluence (amount of radiation delivered per unit of time) of the source. Use of X-ray irradiation for manufacturing purposes such as the manufacture of heat-shrink tubing for electronics is also known.
For sterilization with gamma radiation, 60Cobalt has been the standard radioisotope of choice. 60Cobalt emits gamma rays at energies of 1.17 MeV and 1.33 MeV. The efficacy of radiation at these energies has been long established for these applications. One of the drawbacks to the use of 60Cobalt is that its higher energy line (1.33 MeV) is above the energy level at which radioactivity is induced. There is a need for an irradiation apparatus whose maximum energy output is below the threshold of 60Cobalt, so as to avoid the problem of inducing radioactivity in material being irradiated. It would further be desirable to provide an apparatus for irradiation that altogether avoids the use of radioisotopes, so as simplify operation and licensing, and eliminate the possibility of diversion of such radioisotopes for illegal purposes.
Prior X-ray sources have not achieved a position of dominance due to the fact that although they can easily achieve higher energies, they have heretofore been unable to economically achieve the fluence of gamma sources. A need exists, therefore, for irradiation apparatus that can simultaneously achieve both the high energy and fluence necessary for practical sterilization, decontamination, and environmental remediation applications.